Traditional medicine has been a fertile source for revealing novel lead molecules for modern drug discovery. In plants, terpenoids represent a chemical defense against environmental stress and provide a repair mechanism for wounds and injuries. Interestingly, effective ingredients in several plant-derived medicinal extracts are also terpenoid compounds of monoterpenoid, sesquiterpenoid, diterpenoid, triterpenoid and carotenoid groups. Inflammatory diseases and cancer are typical therapeutic indications of traditional medicines. Thus folk medicine supports the studies which have demonstrated that plant-derived terpenoid ingredients can suppress nuclear factor-kappaB (NF-kappaB) signaling, the major regulator in the pathogenesis of inflammatory diseases and cancer.We review the extensive literature on the different types of terpenoid molecules, totalling 43, which have been verified both inhibiting the NF-kappaB signaling and suppressing the process of inflammation and cancer. It seems that during evolution, plants have established a terpene-based host defense which also represents a cornucopia of effective therapeutic compounds for common human diseases.